Tube sealing



Jan. 8, 1957 H. J- DAILEY ET AL TUBE SEALING Filed April 29, 1952 INVENTORS United .States VPatent TUBE SEALING HamptonJ. Dailey, deceasedylate of -'Verona',-N."J.',=fby Ruth M. Dailey, executrix, Verona, N. J., and William J. Knochel, East Orange, N. J., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 29, 1952, Serial No. 284,911

This invention relates to tube sealing and more specically to cold pressure welding of tubes of cold rolled steel.

There are numerous instances of use of cold rolled steel tubing which require a permanent and non-leaking seal at the end of the tube, such as with the charging tubulation with refrigerators or the evacuation tubulaftion of ignitrons. For such reasons as strength in the tubulation or avoiding contamination of the contents of the tubulation, use of cold rolled steel is often highly desirable and oft-times imperative. Heretofore, where permissible, copper tubing has been employed because it could be pinched off with a tight seal resulting. Cold rolled steel tubing could not be substituted for the copper and pinched off, because it would not make a tight seal due to crevices and non-welding of the steel by pressure only. The present invention proposes a means and method of effecting a seal of cold rolled steel tubing by a cold pinch-olf.

More specifically, an object of the invention is to provide a cold pinch-olf for cold rolled steel tubing that will be vacuum tight.

Another object of the invention is to provide such a seal as above-mentioned without contamination of the interior tube surface by presence within the tube of other than the surface of the cold rolled steel of the tubing.

Other objects of the invention will appear to persons skilled in the art to which it appertains, as the description proceeds, both by direct recitation and by implication from the context.

Referring to the accompanying drawing in which like numerals of reference indicate similar parts throughout the several views:

Figure l is a sectional View of a tube and pinching jaws ready for the pinch-off operation;

Figure 2 is a section at right angles to Figure 1 as on line I-I thereof;

Figure 3 is a sectional view similar to Figure l but showing the pinch-off as having been effected;

Figure 4 is a cross section of tube and of a modified form of sealing medium applied thereto ready for the pinch-olf operation as in Figure 2; and

Figure 5 is a greatly magnified longitudinal section of the pinched-olf end of tubing in accordance with the present invention.

In the specific embodiment of the invention illustrated in said drawing, the reference numerals and 11 designate pinching jaws, and for convenience in distinguishing one from the other these will be more particularly designated upper and lower jaws respectively. Said jaws' Votherfside `of the jaws.

- 2,776,473 Ice Patented Jan. 8, v1957 A certain amount of cold ilow of the metal of which the tubing is composed takes place in this pinching operation, but with cold rolled steel tubing it is found that the metal does not coldflow or weld together under this cold pressure pinching, and crevices remain which keep the tubing from being vacuum tight.

We have found that a perfectly tight vacuum seal can be Vobtained with cold rolled steel tubing by simultaneously pinching therewith a sealing medium 13 of a more ductile metal, of which tin, zinc and copper are examples. Preferably oxygen free high conductivity copper is used. This medium may be variously positioned at the place where the pinch-off is to be eected. For instance, the medium may be a sleeve slipped onto the steel tubing, or it may be an electro or otherwise deposited layer of copper or other ductile metal, or a combination of a deposited layer on the steel and a sleeve thereover. Another mode of locating the sealing medium at the place where the pinch-off is to be effected is shown in Fig. 4 wherein said medium is of U-shape so it can be slipped onto the tubing from the side with the legs of the U interposed between the tubing and the respective jaws of the pinching mechanism.

The tubing, with the sealing medium in juxtaposition thereto is placed between the pinching jaws and pinched to the extent that the jaws come together and sever the tube thereat. The pinching operation results in cold ow of the metal where pressed by the jaws, and while it is found that cold rolled steel treated in this manner makes an imperfect seal from the standpoint of vacuum-tightness, the juxtaposed sealing medium metal will be intimately bonded with the steel at the interfaces where the pressure has been applied and the sealing medium will weld or unify with itself at the tip 14 of the pinched-olf tubing and make a perfect Vacuum-tight seal thereat. The sealing medium 13 applied and cold welded as thus described is at the outside of the tubing and the interior of the tubing remains strictly a steel surface without the slightest contamination from the sealing medium. The seal thus made furthermore has the advantage of the strength of the steel to keep the seal closed to its squeezed or pinched condition and no rupturing strain is applied in use on the sealing medium which therefore will function indefinitely to maintain the pinched-olf seal hermetically tight.

We claim:

1. A method of sealing hard metal tubing comprising applying a soft-metal sealing medium at the location of seal on the exterior of the tubing, cold pressing the tubing and medium simultaneously to pinch-off both together and compressing the sealing medium beyond the end of the pressed tubing and unifying said medium where extending beyond said tubing for effecting a tight seal at said end.

2. A method of effecting an impervious seal for a hard-metal tubing having a cylindrical wall, comprising applying a sealing medium of cold-weld type of metal on the exterior of said tubing at the location of the proposed seal, cold pressing said tubing and medium simultaneously until said tubing is converged to a point and severed thereat, and continuing the cold pressing and converging the sealing medium into an integral termination projecting axially beyond the converged and severed end of said tubing and effecting a hermetic seal therefor.

3. A method of sealing hard-metal tubing, said method including the steps of applying a first layer of a soft-metal sealing medium on the exterior of said tubing at the location of the seal, applying a second layer of a soft-metal sealing medium on the exterior of said rst layer at location of said seal, cold pressing said tubing References Cited in the file of this patent UNITED STATES PATENTS Eden et al. June 20, 1933 Young Jan. 13, 1942 Herzog Mar. 7, 1944 Ris Oct. 16, 1945 Garner et a1. Sept. 16, 1947 Sowter Sept. 12, 1950 Grimes May 22, 1951 

